1. Field of the Invention
The present invention relates to imaging apparatuses, and in particular, to processing for converting the number of pixels of an input image signal.
2. Description of the Related Art
Conventionally, enlargement or reduction processing is known in which an image signal corresponding to a predetermined number of pixels is obtained by performing enlargement or reduction processing on an image signal corresponding to a certain resolution (certain number of pixels). Camcorders are one type of known apparatus that performs such enlargement or reduction processing.
In conventional camcorders, an image signal corresponding to a predetermined number of pixels which is defined by a format is acquired by an imaging device, and is recorded on a tape. Comcorders commonly have a function called “electronic zooming” in addition to normal optical zooming. In electronic zooming, the above enlargement processing is performed on part of an image signal from the imaging device.
In addition, recently, with the progress of semiconductor technology, a type of apparatus for recording high quality images has been proposed that employs an imaging device having a number of pixels which is much greater than the number of pixels defined by the format used in conventional comcorders and that generates an image signal corresponding to the number of pixels defined by the conventional format by performing reduction processing on the image signal from the imaging device. In this type of apparatus, while the zooming magnification is low (when optical zooming is being performed), an image signal output from the imaging device is processed for reduction, and is processed for enlargement by a higher magnification as the electronic zooming magnification increases. In this technique, in VCRs having an imaging device with a large number of pixels, the quality of images to be recorded can be enhanced.
However, although a type of camcorder having an imaging device with a large number of pixels can record high quality images, their circuit size is large because image processing must be performed for enlargement and reduction by arbitrary factors.
Even conventional camcorders also have a large circuit size when performing enlargement and reduction processing by arbitrary factors.
In any of these types of apparatuses, in order that high quality enlarged or reduced images may be obtained, coefficients of filters for use in enlargement and reduction processing must be variably set, and filters having a large number of taps must be used. This causes a much larger circuit size than that of a case of performing only one of enlargement processing and reduction processing, and is an obstacle to the development of inexpensive high-image-quality apparatuses.